6 volts in 2-AA space?

[georget98]

I bought a couple of cheap keychain LED lights on ebay ($1.99 each) to give to people that had liked my Photon light. I know it's a cheap trick, but people that would appreciate the real thing have already bought them...

Well, the seller sent me an extra light and threw in a few blue LEDs, too. So I put a blue in the extra light, and now I have a reasonably bright white LED left over, my first!

It's not quite as bright as my Arc AAA but we've all got to start someplace.

Well, now I want to put it in my Mini you know what Lite to change it from yellow to white. The keychain lights have two 3 volt lithium coin cells, so I need 6 volts in the space of 2 AAs.

I pictured 4 N cells neatly lined up, but checked the specs and they're too long. I guess I should build some sort of step up converter, but I'm not quite up to it yet.

Are there any other sort of batteries I can put in that space to make 6 volts? Maybe some sort of camera battery that has two 1/2-AAs inside?

 

[x-ray]

Another member (ab) recently discovered that Energizer CRV3 batteries contain 2x 3v AA size connected in parallel.

Read this thread for details.

<font color="red">*NOTE - READ THE WHOLE THREAD

It appears that only the Japanese versions of these batteries contain 3v AA's (versions manufacturered elsewhere seem to contain 2x 1.5v AA's in series)</font>

For more details also look here.

 

[highlandsun]

There's a variety of different Lithium-based battery chemistries available in 3V AA cells. Saft & Tadiran are good places to start looking. You may also find Japanese-made CRV3's for cannibalizing, it's been mentioned in another thread here before.

 

[bdl666]

Try using Lr44's. Four of them will drive the led. I sort of did the same as you want to do but I used a cheap dollar store AA MiniMag rip off. But I used 6 Lr44 and am driving it at 9v.Just tape them all in series and find a spring to fill the rest of the space.

 

[Kill-O-Zap]

georget98,

I suspect 6V is going to overdrive, and likely fry your LED; 6V nominal from AA sized cells is different from 6V nominal from button cells; the button cells will drop in voltage under load much more than the AA's.

There are tons of threads on CPF regarding how to mod a Mini to with a single blue or white LED, and feeding it the proper voltage; people have done 2N cells + 1AA; they've done 2/3 AA and 1/2 AA NiCads, and who knows what else. If you go the 1/2 CRV3 route, I would suggest using one of those beasties, plus one 1.5V Alkaline for a total of ~4.5V which is still a LOT for a white LED.

Good luck,
Sal

 

[JSWrightOC]

Typically it is not wise to mix and match battery chemistries in a circuit. This is mostly because different chemistries can source varying amounts of current (for a given form factor) and have different capacities. It's like mixing unmatched NiCd cells together and expecting not to reverse pol a cell. It can be done in a pinch if you check your batts often, but I would not recommend it.

If you are interested in LED driving circuits, there are numerous step-up DC-DC inverter circuits available for driving at many current levels.

 

[Christoph]

All the cr-v3's that I checked were duracell brand and all were 3 volt aa cells
Chris

 

[Kill-O-Zap]

What JSWrightOC writes about mixing battery types is true but I would really not be too concerned about this in a <50ma draw application such as a 1-led mod. But if you burn down the house, I disclaim any responsibility /ubbthreads/images/graemlins/grin.gif

--Sal

 

[JSWrightOC]

Yes, you are right. Also, if you keep an eye on cell voltage and replace the low ones as needed you'll be fine. Is there no cleaner way to do it? I still think a step-up inverter would work best, it would also be the cleanest design. No kluges!!

 

[Kill-O-Zap]

Agreed, mixing batteries is a major kluge. Step-up inverter is the way I would go. But then I would also go with an LS. And Brinkmann instead of the leading brand. Oh wait, I already did all that, a couple of times, with some help from dat2zip /ubbthreads/images/graemlins/smirk.gif

 

[JSWrightOC]

[ QUOTE ]
Kill-O-Zap said:
Oh wait, I already did all that, a couple of times, with some help from dat2zip /ubbthreads/images/graemlins/smirk.gif

[/ QUOTE ]

/ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif

he he he...we all love his stuff, I just ordered *another* BB400, this one with a Q3L upgrade. I'm a FLASHAHOLIC already!!!

I hand the light to everyone at work here, and the first thing they do is point it at their face and turn it on. The reactions are hilarious!!!

 

[georget98]

[ QUOTE ]
Kill-O-Zap said:
I suspect 6V is going to overdrive, and likely fry your LED; 6V nominal from AA sized cells is different from 6V nominal from button cells; the button cells will drop in voltage under load much more than the AA's.

[/ QUOTE ]

I wondered about that, too. I remember always putting a limiting resistor in LED circuits.

I had a spare blue so I hooked it up to 4-AAs. It was nice and bright /ubbthreads/images/graemlins/cool.gif, "ouch that's hot /ubbthreads/images/graemlins/ooo.gif, "hey it went out /ubbthreads/images/graemlins/icon23.gif"

I think I'll look at building a step-up converter. I assume circuit diagrams abound here.